irAE T1DM Incidence — SCE Medical Oncology MCQ

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ModerateMelanoma & SkinirAE T1DM IncidenceSCE Medical Oncology

A 60-year-old man with metastatic melanoma develops new-onset diabetes mellitus on ICI. His GAD65 antibodies are positive. He is stabilised on insulin. What proportion of patients develop new-onset type 1 diabetes as an irAE?

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Correct answer: E — Approximately 0.2-1%

ICI-induced type 1 diabetes occurs in approximately 0.2-1% of patients, more commonly with anti-PD-1 than anti-CTLA-4. It results from immune-mediated destruction of pancreatic beta-cells. Features: acute onset (can present with DKA), low/undetectable C-peptide, positive islet autoantibodies (GAD65, IA-2, ZnT8) in ~50%. Unlike most irAEs, it is irreversible and requires lifelong insulin replacement. Corticosteroids do NOT restore beta-cell function. ICI can be continued once diabetes is well controlled on insulin.

Reference: https://www.nice.org.uk/guidance/conditions-and-diseases/cancer